In a representative zone structure for a cellular communication system, such as is illustrated in FIG. 3A-3C, a repeating pattern is formed with a number of hexagonal cells or zones; e.g., four cells in FIG. 3A, seven cells in FIG. 3B, and 12 cells in FIG. 3C. In each cell pattern, the same control channel, or number of control channels, is allotted to each cell having the same designation (in this instance, the same digit 1-12) assigned thereto. No two adjacent cells are assigned the same designation and control channels, in order to avoid the effects of local interference. The number of control channels allotted to each cell is pre-assigned in a fixed manner.
For a microcellular system (MCS), it has been usual to allot control channels for each service area in a fixed manner, similar to the system employed for an ordinary cellular system described above. However, when applying the standard control channel allotting method to an MCS, problems are encountered. For example, it is difficult to arrange cells in an MCS in a regular manner, such as the hexagonal layout shown in FIGS. 3A-3C, and is correspondingly difficult, therefore, to allot control channels in a fixed manner. Furthermore, since the number of zones to be covered differs greatly for each MCS, there are many cases in which the number of channels required must be changed for each such system. A mobile unit seeking to obtain service in one of a plurality of MCS's must, consequently, store information relating to all of the control channels which might be used and must search all of the stored control channels in order to find the control channels allotted to the local MCS for each use. The time involved in such searching significantly inhibits usage of a mobile unit.
It is, therefore, an objective of the present invention to provide a method of use of a control channel in an MCS in which a required control channel or channels may be arbitrarily selected depending upon the conditions under which the MCS is to be used.
It is a further objective of the invention to provide a method of use of a control channel whereby a mobile unit can locate a control channel for the MCS in a minimum search time.